Tire

Abstract

The tire (10) includes a width-direction narrow groove (8) extending in the tread surface (11) and having a width-direction component. The width-direction narrow groove (8) has a center-side narrow groove portion (8a) located inside the tire width direction and a shoulder-side narrow groove portion (8b) continuous outside the tire width direction. The center-side narrow groove portion (8a) has the following shape: a narrow width portion (8au) including the groove opening, a tapered portion (8at) whose groove width increases towards the groove bottom, a wide straight portion (8as) extending along the groove depth direction with a constant groove width greater than the narrow width portion, and an arcuate portion (8ab) including the groove bottom are continuously connected from the groove opening side to the groove bottom side. The shoulder-side narrow groove portion (8b) has the following shape: a narrow width portion (8bu) including the groove opening, a tapered portion (8bt) whose groove width increases towards the groove bottom, and an arcuate portion (8bb) including the groove bottom are continuously connected from the groove opening side to the groove bottom side.

Description

Technical Field

[0001] This disclosure relates to tires.

[0002] This application claims priority based on Japan Patent Application No. 2021-202052, filed on December 13, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0003] In particular, in tires used for construction and mining vehicles that transport ore and topsoil in mines and other similar locations, especially in tires for construction and mining vehicles (mainly used for mining copper, iron, etc.) that are suitable for operation on relatively firm surfaces, relatively narrow grooves can be provided primarily in the tread to increase the rubber volume in the tread and improve wear life.

[0004] For example, Patent Document 1 discloses a tire (OR) for a construction vehicle having a relatively narrow groove extending in the tread along the width direction of the tire.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-001449 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, narrower groove widths in the tread are often prone to causing more separation between the tread rubber and the belts (known as cut separation) due to cuts from the road surface. As a result, the overall tire life may not be adequately improved, and there is still room for improvement in the conventional techniques described above.

[0010] Therefore, the purpose of this disclosure is to provide a tire that suppresses cut separation while maintaining sufficient wear life.

[0011] Solution for solving the problem

[0012] The tire disclosed herein includes a narrow groove in the width direction extending in a component of the tire width direction on the tread surface, characterized in that,

[0013] The width-direction narrow groove has a center-side narrow groove portion located on the inner side in the tire width direction and a shoulder-side narrow groove portion connected to the outer side in the tire width direction of the center-side narrow groove portion.

[0014] In a cross-sectional view perpendicular to the extension direction of the central narrow groove, the central narrow groove is formed from the groove opening side to the groove bottom side into the following continuously connected segments: a narrow segment including the groove opening; a tapered segment whose groove width increases towards the groove bottom; a wide straight segment extending along the groove depth direction with a constant groove width and whose groove width is greater than that of the narrow segment; and an arc-shaped segment including the groove bottom.

[0015] In a cross-sectional view perpendicular to the extension direction of the narrow groove on the tire shoulder side, the narrow groove on the tire shoulder side is formed from the groove opening side to the groove bottom side into the following continuously connected segments: a narrow segment including the groove opening; a tapered segment whose groove width increases toward the groove bottom; and an arcuate segment including the groove bottom.

[0016] The effects of the invention

[0017] According to this disclosure, a tire can be provided that suppresses cut separation while maintaining sufficient wear life. Attached Figure Description

[0018] [ Figure 1 ] Figure 1 This is a unfolded view showing the tread surface of a tire according to one embodiment of the present disclosure.

[0019] [ Figure 2 ] Figure 2 (a) is along Figure 1 A cross-sectional view of line AA in the diagram. Figure 2 (b) is along Figure 1 A cross-sectional view of line BB in the diagram.

[0020] [ Figure 3 ] Figure 3 It is along Figure 1 A partial cross-sectional view of the tire width direction of the tire half of line XX.

[0021] [ Figure 4 ] Figure 4 This is a schematic diagram illustrating the reason for the cutting and separation.

[0022] [ Figure 5 ] Figure 5 (a) is a graph showing the relationship between rolling distance and circumferential shear strain in the tires of the comparative example. Figure 5 (b) is a graph showing the relationship between rolling distance and circumferential shear strain in the tire of the invention example. Detailed Implementation

[0023] The tires disclosed herein can be applied to any type of tire, and are particularly suitable for pneumatic tires used in construction and mining vehicles that transport ore and topsoil in mines and the like, especially tires suitable for construction and mining vehicles (mainly used for mining copper, iron, etc.) that operate on relatively firm surfaces and good roads.

[0024] In the following description, embodiments of the tire according to the present disclosure will be illustrated with reference to the accompanying drawings.

[0025] In all the drawings, common parts and components are marked with the same reference numerals / symbols.

[0026] In this document, the term "tire circumferential" refers to the direction in which the tire rotates about its axis of rotation, the term "tire radial" refers to the direction perpendicular to the tire's axis of rotation, and the term "tire width direction" refers to the direction parallel to the tire's axis of rotation. In some accompanying drawings, the tire circumferential direction is indicated by the symbol "CD", the tire radial direction by the symbol "RD", and the tire width direction by the symbol "CD".

[0027] In addition, in this paper, the side closer to the tire equator CL along the tire width direction is called the "inner side in the tire width direction", and the side farther away from the tire equator CL along the tire width direction is called the "outer side in the tire width direction".

[0028] Figures 1 to 3 This is a drawing illustrating a tire 10 according to one embodiment of the present disclosure.

[0029] Figure 1 This is a unfolded view showing the tread surface of a tire according to one embodiment of the present disclosure. Figure 2 (a) is along Figure 1 A cross-sectional view of line AA in the diagram. Figure 2 (b) is along Figure 1 A cross-sectional view of line BB in the diagram. Figure 3 It is along Figure 1 A partial cross-sectional view of the tire half of line XX in the tire width direction (more specifically, from...) Figure 1 (A cross-sectional view of the tire half on the side opposite the tire equatorial plane CL, cut from the centerline of the narrow-width directional groove 81 and the lateral tread groove 91 in the tire).

[0030] It should be noted that the tire of this disclosure can be constructed as any type of tire; however, the tire in this embodiment is constructed as a tire for construction and mining vehicles.

[0031] In the following text, unless otherwise stated, the positional relationships and dimensions of each element shall be measured under the reference condition of the tire mounted on an applicable rim, inflated to the specified internal pressure, and unloaded. Furthermore, under the condition of the tire mounted on an applicable rim, inflated to the specified internal pressure, and under maximum load, the width of the contact patch in the tire width direction is referred to as the "tread width (TW)," and the edge of the contact patch in the tire width direction shall be referred to as the "tread end (TE)."

[0032] As used herein, the term "applicable rim" refers to a standard rim of applicable size (measured rim in the ETRTO Standards Manual and designed rim in the TRA Yearbook) that is recorded or may be recorded in the future in an industry standard in effect in the region where the tire is manufactured and used. Such industry standards include, for example, the JATMA Yearbook of Japan's JATMA (Japan Automobile Tire Manufacturers Association), the standards manual of Europe's ETRTO (European Tire and Rim Technology Organization), and the yearbook of the US's TRA (Tire and Rim Association). For sizes not listed in these industry standards, "applicable rim" refers to a rim whose width corresponds to the bead width of the pneumatic tire. "Applicable rim" includes current sizes in the aforementioned industry standards as well as future sizes to be listed. An example of a "future-detailed size" could be a size listed as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO.

[0033] As used herein, the term "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating, as described in industry standards such as the aforementioned JATMA Yearbook. For sizes not listed in the aforementioned industry standards, the term "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle with the tire mounted. Furthermore, as used herein, the term "maximum load" refers to the load corresponding to the maximum load capacity of a tire of the applicable size described in the aforementioned industry standards, or, for sizes not listed in the aforementioned industry standards, the load corresponding to the maximum load capacity specified for each vehicle with the tire mounted.

[0034] In this document, the term "groove width" shall be measured in the aforementioned reference condition, in a section perpendicular to the groove extension direction at the tread surface, along a direction parallel to the tread surface. The groove width may vary in the direction perpendicular to the tread surface. Additionally, as used herein, the term "groove depth direction" refers to the direction perpendicular to the tread surface in the aforementioned reference condition, and the "groove depth" herein shall be measured in the aforementioned reference condition in the direction perpendicular to the tread surface.

[0035] like Figure 3As shown, a tire 10 according to one embodiment of the present disclosure includes a tread portion 1, a pair of sidewall portions 2 extending radially inward from both ends of the tread portion 1 in the tire width direction, and a pair of bead portions 3 disposed at the inner ends of each sidewall portion 2 in the tire radial direction.

[0036] Additionally, tire 10 includes a pair of bead cores 3a, a carcass 4, a belt 5, a bead wrap 6, and tread rubber 1a. Tire 10 may have an inner liner (not shown) on its innermost surface.

[0037] Although Figure 3 The diagram shows one half of tire 10, but the other half of tire 10 has the same construction. However, the other half of tire 10 can be constructed differently from the tire half on one side.

[0038] Each bead core 3a is embedded in a corresponding bead portion 3. The bead core 3a includes a plurality of bead lines surrounded by a rubber coating. However, the bead core 3a may consist of a single bead line. Preferably, the bead line is made of metal (e.g., steel). The bead line may be, for example, made of monofilament or twisted thread. It should be noted that the bead line may be made of organic or carbon fiber.

[0039] The carcass 4 spans between a pair of bead cores 3a and extends annularly through a pair of sidewall portions 2 and the tread portion 1. The carcass 4 is composed of at least one (in this example, one) carcass cord layer made of rubber-coated carcass cords. The carcass cords may be formed, for example, from monofilaments or twisted yarns.

[0040] In this embodiment, the carcass cords are made of metal (e.g., steel). However, the carcass cords can also be made of organic fibers such as polyester, nylon, rayon, or aramid. Furthermore, in this embodiment, the carcass 4 is a radial carcass, but it can also be a bias carcass. In this embodiment, the carcass 4 has a ply body portion and a ply fold-back portion located between a pair of bead cores 3a. This ply fold-back portion folds back from both ends of the ply body portion around the bead cores 3a along the tire width direction from the inside to the outside. However, the folding method of the carcass 4 is not limited; for example, the carcass 4 can be wound around the bead cores 3a or may not have a ply fold-back portion. It should be noted that the bead portion 3 may be provided with a bead wrap (not shown) to protect the carcass 4.

[0041] The belt 5 is arranged on the outer side of the tire crown in the tire radial direction relative to the tire carcass 4. The belt 5 includes at least one belt layer composed of rubber-coated belt cords arranged at a predetermined angle relative to the tire circumference. Figure 3 As shown, in this example, the belt 5 consists of six belt layers 5a, 5b, 5c, 5d, 5e and 5f.

[0042] In this embodiment, of the six belt layers 5a to 5f, the two belt layers 5a and 5b closest to the tire carcass 4 are formed to have a relatively narrow width in the tire width direction (e.g., 34% to 63% of the tread width TW). Furthermore, the belt cords constituting the two belt layers 5a and 5b intersect each other and are inclined at a relatively small angle (e.g., 4° to 10°) relative to the tire circumference. These allow the belts 5 (more specifically, belt layers 5a and 5b) to exert a so-called "tagger" effect and withstand sufficient tension in the tire circumference to suppress diameter growth in the tread portion 1.

[0043] In this embodiment, on the other hand, of the six belt layers 5a to 5f, the four belt layers 5c, 5d, 5e, and 5f closest to the tread surface 11 are formed to have a relatively wide width in the tire width direction (e.g., 75% to 100% of the tread width TW). Furthermore, the belt cords constituting the four belt layers 5c, 5d, 5e, and 5f intersect each other between at least any two layers and are inclined at a relatively large angle (e.g., 18° to 35°) relative to the tire circumference. These features can suppress stress concentration and separation at the tire width direction edges of the two belt layers 5a and 5b closest to the tire carcass 4, and thus suppress the decline in tire durability.

[0044] In this embodiment, the belt cord is made of metal (e.g., steel); however, the belt cord may be made of organic fibers such as polyester, nylon, rayon, or aramid.

[0045] The tread rubber 1a is located in the tread portion 1, on the outer side of the tire in the radial direction of the belt 5. The tread rubber 1a constitutes the tread surface 11, which is the outer surface of the tread portion 1 in the radial direction of the tire. This will be described below. Figure 1 The tread pattern shown is formed on the tread surface 11.

[0046] The tread pattern of a tire 10 according to one embodiment of the present disclosure will now be described.

[0047] like Figure 1As shown, the tire 10 of this embodiment has: three circumferential narrow grooves 7 (71, 72, 73) extending in a circumferential component (in this example, extending along the tire circumferential direction (i.e., without tilting relative to the tire circumferential direction)) (hereinafter also referred to as "extending in the tire circumferential direction"); width-direction narrow grooves 8 (81, 82, 83, 84) extending in a width-direction component (hereinafter also referred to as "extending in the tire width direction"); and lateral lug grooves 9 (91, 92) also extending in a width-direction component. The tread pattern of the tread surface 11 is a block pattern, wherein the tread surface 11 is divided into blocks by these circumferential narrow grooves 7, width-direction narrow grooves 8, and lateral lug grooves 9. Additionally, as... Figure 1 As shown, the tread patterns of the two halves of the tire, separated by the tire's equatorial plane CL, are slightly offset from each other in the tire's circumferential direction; however, they are essentially the same in other respects. That is, in the unfolded diagram of the tread surface, the tread patterns of the two halves can be superimposed on the other by moving one side parallel and linearly symmetrically.

[0048] However, in this embodiment, the tread pattern is not limited, as long as the tread surface 11 has a narrow groove 8 in the width direction.

[0049] In this embodiment, such as Figure 1 As shown, the circumferential narrow groove 72 extends along and across the tire equatorial plane CL. Circumferential narrow grooves 71 and 73 are spaced apart from the circumferential narrow groove 72 on each side of the circumferential narrow groove 72 in the tire width direction.

[0050] like Figure 1 As shown, the width-direction narrow grooves 81 to 84 extend along the tire width direction between the aforementioned circumferential narrow grooves 72 and 71 or between the aforementioned circumferential narrow grooves 72 and 73, respectively, to connect these circumferential grooves.

[0051] In this example, the width-direction narrow groove 81 differs from the width-direction narrow groove 82 only in that it has a second shoulder-side narrow groove portion 81c, which will be described later. The width-direction narrow grooves 81 and 82 are arranged alternately at approximately equal intervals on one side of the tire equatorial plane CL in the tire circumferential direction. Furthermore, in this example, the width-direction narrow groove 83 differs from the width-direction narrow groove 84 only in that it has a second shoulder-side narrow groove portion 83c, which will be described later. The width-direction narrow grooves 83 and 84 are arranged alternately at approximately equal intervals on the other side of the tire equatorial plane CL in the tire circumferential direction.

[0052] like Figure 1 As shown in the unfolded view of the tread surface 11, the width-direction narrow grooves 81 to 84 extend in the tire width direction with a curved, approximately S-shaped pattern. However, the width-direction narrow grooves 81 to 84 do not need to extend in a curved pattern; for example, they can extend in a straight pattern.

[0053] Here, in this document, the term "narrow groove" (e.g., circumferential narrow groove or width-direction narrow groove) refers to a groove in which, when the tire is mounted on a suitable rim, filled with a specified internal pressure, and under maximum load, the groove walls at least partially contact and close each other in the groove depth direction. Especially when the tire 10 is a very large pneumatic tire for construction and mining vehicles, for example in this embodiment, from the viewpoint of ensuring sufficient drainage and cooling performance, as well as ensuring rubber volume and suppressing a decrease in the rigidity of the tread 1, the width-direction narrow grooves 8 (81 to 84) preferably have a groove width of 3 mm to 18 mm, more preferably 5 mm to 15 mm.

[0054] like Figure 1 As shown, lateral tread grooves 91 and 92 extend from circumferential narrow grooves 71 or 72 along the tire width direction on the outer shoulder portion of the tread surface 11 in the tire width direction and reach the tread end TE. Lateral tread groove 91 connects to circumferential narrow groove 71 and width direction narrow groove 81. Furthermore, lateral tread groove 92 connects to circumferential narrow groove 73 and width direction narrow groove 83.

[0055] In this embodiment, such as Figure 1 and Figure 2 As shown, each of the width-direction narrow grooves 8 (81 to 84) has a center-side narrow groove portion 8a (81a to 84a) located on the inner side in the tire width direction and a shoulder-side narrow groove portion 8b (81b to 84b) connected to the center-side narrow groove portion 8a (81a to 84a) on the outer side in the tire width direction.

[0056] Here, "center side narrow groove 8a located on the inner side in the tire width direction" means that, compared with the shoulder side narrow groove 8b, the center side narrow groove 8a is located on the inner side in the tire width direction.

[0057] In this example, such as Figure 1 and Figure 3 As shown, the dividing position in the tire width direction between the center-side narrow groove 8a (81a to 84a) and the shoulder-side narrow groove 8b (81b to 84b) on the tread surface 11 is the 1 / 8 point P1 / 8, which will be described later. However, the dividing position in the tire width direction does not have to be the 1 / 8 point P1 / 8. In this example, as... Figure 3 As shown, the center side narrow groove 8a (81a) and the shoulder side narrow groove 8b (81b) switch almost abruptly, with virtually no transition area between them.

[0058] like Figure 2As shown in (a), in a cross-sectional view perpendicular to the extension direction of the central narrow groove on the tread surface 11, the central narrow groove 8a (81a to 84a) of the width direction narrow groove 8 (81 to 84) is formed from the groove opening side to the groove bottom side in the following continuously connected segments: a narrow segment 8au including the groove opening; a tapered segment 8at whose groove width W2 increases toward the groove bottom; a wide straight segment 8as extending along the groove depth direction with a constant groove width W3 and whose groove width is greater than that of the narrow segment 8au; and an arcuate segment 8ab including the groove bottom. In other words, in the above cross-sectional view, the central narrow groove 8a is formed in the shape of a paddle (such as a paddle for paddling a canoe).

[0059] The narrow segment 8au includes a groove opening, that is, it is positioned closest to the tread surface 11. For example... Figure 2 As shown in (a), in this example, the narrow segment 8au has two straight groove walls in the cross-sectional view along the groove depth direction, and extends with a constant and relatively small groove width W1 in the groove depth direction. In this example, the narrow segment 8au is formed with a groove width W1 such that when the tire is mounted on a suitable rim, filled with a specified internal pressure, and loaded with a maximum load, at least some of the groove walls contact each other and close. However, the cross-sectional shape of the narrow segment 8au is not particularly limited to the shape described above.

[0060] The tapered segment 8at continuously connects to the bottom side of the narrow segment 8au in the groove depth direction. The tapered segment 8at is formed such that the groove width W2 increases towards the bottom side of the groove, that is, the two groove walls narrow in a contracting manner in the cross-sectional view. Figure 2 As shown in (a), in this example, the tapered segment 8at has two groove walls that extend linearly in the groove depth direction in the cross-sectional view, but the two groove walls may extend curvedly (e.g., arc-shaped) in the groove depth direction. Furthermore, in this example, the tapered segment 8at is formed such that the groove width W2 gradually (i.e., continuously) increases toward the groove bottom; however, it can be formed such that the groove width W2 increases intermittently (i.e., discontinuously at a given position in the groove depth direction) toward the groove bottom.

[0061] The wide, straight section 8as is continuously connected to the bottom side of the tapered section 8at in the groove depth direction. In the wide, straight section 8as, the two groove walls are straight in cross-sectional view (more specifically, they extend in a straight line along the groove depth direction, i.e., parallel to the groove depth direction). This section extends with a constant and relatively large groove width W3 in the groove depth direction. The groove width W3 of the wide, straight section 8as is greater than the groove width W1 of the narrow section 8au (more specifically, greater than the maximum groove width W1 of the narrow section 8au).

[0062] The arc-shaped segment 8ab includes the bottom of the groove; that is, the arc-shaped segment is closest to the bottom of the groove. The arc-shaped segment 8ab is continuously connected to the bottom side of the wide straight segment 8as in the groove depth direction. For example... Figure 2As shown in (a), in this example, the arc segment 8ab is formed by a single arc that is approximately semicircular in the cross-sectional view; however, it does not necessarily have to be formed by a single arc in the cross-sectional view. For example, it can be formed by multiple interconnected arcs (and thus be a smooth curved shape).

[0063] In this embodiment, such as Figure 2 As shown in (a), the boundary portions of the narrow segment 8au, the tapered segment 8at, and the wide straight segment 8as of the central side narrow groove 8a are angled in the cross-sectional view. However, from the perspective of suppressing stress concentration at the boundary portions, the boundary portions between the narrow segment 8au, the tapered segment 8at, the wide straight segment 8as, and the arc segment 8ab can be circular in the cross-sectional view.

[0064] like Figure 2 As shown in (b), in a cross-sectional view perpendicular to the extension direction of the shoulder-side narrow groove 8b on the tread surface 11, the shoulder-side narrow groove 8b (81b to 84b) of the width direction narrow groove 8 (81 to 84) is formed from the groove opening side to the groove bottom side in the following continuously connected segments: a narrow segment 8bu including the groove opening; a tapered segment 8bt whose groove width W2 increases toward the groove bottom; and an arcuate segment 8bb including the groove bottom. In other words, in the above cross-sectional view, the shoulder-side narrow groove 8b is formed in the shape of a flask.

[0065] The cross-sectional shape of the shoulder-side narrow groove 8b differs from that of the center-side narrow groove 8a only in that it does not have a segment corresponding to the wide, straight segment 8as in the center-side narrow groove 8a, and is otherwise substantially the same as the center-side narrow groove 8a. That is, the narrow segment 8bu of the shoulder-side narrow groove 8b and the narrow segment 8au of the center-side narrow groove 8a, the tapered segment 8bt of the shoulder-side narrow groove 8b and the tapered segment 8at of the center-side narrow groove 8a, and the arcuate segment 8bb of the shoulder-side narrow groove 8b and the arcuate segment 8ab of the center-side narrow groove 8a each have substantially the same cross-sectional shape, therefore their description is omitted.

[0066] In this embodiment, such as Figure 2 As shown in (b), in the cross-sectional view, the boundary between the narrow segment 8bu and the tapered segment 8bt of the shoulder-side narrow groove 8b is at an angle. However, from the perspective of suppressing stress concentration at the boundary, the boundary between the narrow segment 8bu, the tapered segment 8bt, and the arc-shaped segment 8bb can be circular in the cross-sectional view.

[0067] It should be noted that, in this embodiment, such as Figure 1 and Figure 3As shown, the width-direction narrow grooves 81 and 83 also have second shoulder-side narrow groove portions 81c and 83c, respectively, which are connected to the outer sides of the shoulder-side narrow groove portions 81b and 83b in the tire width direction. The cross-sectional shape of the second shoulder-side narrow groove portions 81c and 83c is not particularly limited, and can be, for example, grooves extending from the groove opening to near the groove bottom with a substantially constant groove width. Furthermore, in the example shown, the second shoulder-side narrow groove portions 81c and 83c are formed as narrow grooves; however, they may not be formed as narrow grooves. Moreover, the width-direction narrow groove 8 does not necessarily have second shoulder-side narrow groove portions 81c and 83c, as with width-direction narrow grooves 82 and 84.

[0068] In the following text, see references Figure 4 Explain the reasons for the cutting and separation, and describe the effects of the above implementation method.

[0069] Figure 4 It is a schematic diagram used to illustrate the reason for the cutting and separation (it can be regarded as a schematic cross-sectional view).

[0070] Cut-and-separation is the separation that occurs between the tread rubber and the belt due to a cut from the road surface. More specifically, cut-and-separation is the phenomenon that occurs when the tread surface is subjected to a cut from a foreign object on the road surface, and after the cut reaches the boundary between the tread rubber and the belt, the shear strain between the tread rubber and the belt causes a wider separation between them, which progresses further along the belt.

[0071] Figure 4 This is a schematic diagram of tire 10 rolling on road surface GR, viewed from the side of tire 10. It is assumed that tire 10 is rotating in the circumferential direction, represented by the symbol CD in the diagram. In this state, since tire 10 contacts the road surface GR under load F, the tread rubber 1a at the contact point is in the belt 5 (more specifically, the belt layer 5f closest to the tread surface 11) (see...). Figure 3 The tire is crushed between itself and the road surface (GR), and expands outward in the circumferential direction (commonly referred to as crush deformation), such as... Figure 4 The double-dotted lines in the diagram illustrate this. This results in large circumferential shear strain between the tread rubber 1a and the belt 5, and if a cut exists that reaches the belt 5, they can spread along the belt 5 and cause a cut separation.

[0072] Here, for example, such as Figure 4As shown, even with relatively narrow grooves on the tread surface 11, the outward expansion (crushing deformation) of the tread rubber 1a in the tire circumferential direction cannot be suppressed. However, when grooves with large widths are provided, the groove walls expand inwards to absorb and suppress the crushing deformation of the tread rubber 1a, and this reduces the circumferential shear strain between the tread rubber 1a and the belt 5, thereby reducing cut separation.

[0073] On the other hand, increasing the groove width of the groove provided in the tread 1 is effective in suppressing the cutting separation as described above; however, it also reduces the rubber volume of the tread and reduces the tread rigidity (block rigidity), resulting in a reduction in the wear life of the tire.

[0074] Additionally, tires used in construction and mining vehicles (e.g., dump truck tires for mining purposes) are typically mounted on the front axle when new and rotated to the rear axle mid-wear. When tires are used on the rear axle during this mid-wear phase, cut-off often occurs. This is because rear-axle mounted tires often receive cuts when they hit rocks or other foreign objects on the road surface that are not visible to the driver, especially when traveling backwards.

[0075] Furthermore, the cutting marks that serve as the starting point for the separation typically occur near the center of the tread surface 11 in the tire width direction. This is because, as mentioned above, the belt layer (e.g., which has a relatively narrow width in the tire width direction and exhibits the so-called webbing effect) Figure 5 The belt layers 5a and 5b are typically placed near the center of the tire width direction on the tread surface 11, and the webbing effect of this belt induces a reverse deep cut.

[0076] In view of the above analysis, according to the tire 10 of this embodiment, since the narrow groove 8 provided on the tread surface 11 in the width direction has a central side narrow groove portion 8a located on the inner side in the tire width direction, and the central side narrow groove portion 8a has a wide straight section 8as that extends along the groove depth direction with a constant groove width and the groove width is greater than the groove width of the narrow section 8a, the crushing deformation of the tread rubber 1a near the center of the tread surface 11 in the tire width direction (where cutting separation is likely to occur) can be completely absorbed by the wide straight section 8as, and thus cutting separation can be effectively suppressed.

[0077] Furthermore, according to the tire 10 of this embodiment, since the wide straight section 8as is located in the middle of the groove depth direction of the narrow groove 8a on the center side, sandwiched between the narrow section 8au, the tapered section 8at and the arc-shaped section 8ab, the rubber volume of the tread 1 is ensured in the early stage of wear, thereby suppressing the decrease in wear life. In the middle stage of wear, when cutting separation may occur, the wide straight section 8as appears, thereby effectively suppressing cutting separation.

[0078] Furthermore, according to the tire 10 of this embodiment, the shoulder side narrow groove 8b connected to the center side narrow groove 8a on the outer side in the tire width direction does not have the same wide straight section as the center side narrow groove 8a, which can maintain sufficient wear life without reducing rubber volume or tread rigidity (block rigidity) (this may occur when a wide straight section is provided).

[0079] Furthermore, according to the tire 10 of this embodiment, the center side narrow groove portion 8a and the shoulder side narrow groove portion 8b of the narrow groove 8 in the width direction both have an arcuate portion 8ab or 8bb including the groove bottom (i.e., located at the groove bottom), which can suppress the groove bottom from cracking.

[0080] Therefore, the tire 10 according to this embodiment can suppress cutting separation while maintaining sufficient wear life.

[0081] The following is a description of a suitable construction of the tire 10 in this embodiment.

[0082] In the tire 10 of this embodiment, in the unfolded view of the tread surface, the position in the tire width direction where the tire width is separated from the tire equatorial plane CL by 1 / 8 of its width ((1 / 8)TW) (obtained by dividing the tread width into 8 equal parts) is called the 1 / 8 point (in Figure 1 and Figure 3 When the center side narrow groove 8a is located in the tire width direction region (i.e., the tire width direction region located on the inner side from the 1 / 8 point, including the 1 / 8 point) between the two 1 / 8 points (i.e., the 1 / 8 points on each side of the tire equatorial plane CL). Since the tire width direction region between the two 1 / 8 points often suffers fatal cuts that become the starting point of cut separation, it is sufficient to arrange the center side narrow groove 8a in this region to effectively suppress cut separation. On the other hand, a shoulder side narrow groove 8b that does not have a wide straight section and effectively maintains wear life is arranged on the outer side of this region in the tire width direction, thereby maintaining wear life more effectively.

[0083] Here, as described above, in this embodiment, the dividing position in the tire width direction between the center-side narrow groove 8a (81a to 84a) and the shoulder-side narrow groove 8b (81b to 84b) on the tread surface 11 is at the 1 / 8 point. In other words, the center-side narrow groove 8a extends over the entire tire width direction region, including the area inside the 1 / 8 point, in each width-direction narrow groove 8.

[0084] However, the center-side narrow groove 8a does not need to be disposed on the entire tire width direction region including the inner side of the 1 / 8 point in the width direction narrow groove 8. The center-side narrow groove 8a can be located in a portion of the tire width direction region including the inner side of the 1 / 8 point in the width direction narrow groove 8. From the viewpoint of sufficiently suppressing cut separation, for example, when the tire width direction position that separates the tread width TW from the tire equatorial plane CL by 3 / 32 ((3 / 32)TW) is called the 3 / 32 point, the center-side narrow groove 8a is preferably disposed at a position in the tire width direction between the inner edge of the width direction narrow groove 8 in the tire width direction and the outer side of the tire width direction, at the position between the 3 / 32 point and the 1 / 8 point.

[0085] However, the configuration range of the center side narrow groove 8a in the tire width direction may not be as described above.

[0086] In the tire 10 of this embodiment, in a cross-sectional view in the tire width direction, the position where the maximum groove depth in the tread 1 is called OTD, and the bottom of the groove with the maximum groove depth portion (BOTD) is connected in a direction parallel to the tread surface 11, is called the OTD position. Figure 2 and Figure 3 When represented by the symbol POTD, the distance D1 in the groove depth direction between the boundary position of the narrow segment 8au and the tapered segment 8at in the central narrow groove 8a and the OTD position POTD (see Figure 2 (a) is preferably 2 / 3 or less of the OTD.

[0087] In the aforementioned tire rotation, the tire is typically used on the front axle, where cut-and-separation occurs less frequently, until the tire is worn to a position in the groove depth direction where the distance in the groove depth direction from the OTD position POTD is approximately 2 / 3 of the OTD. Therefore, by setting the distance D1 in the groove depth direction between the boundary position of the narrow segment 8au and the tapered segment 8at in the center-side narrow groove 8a and the OTD position POTD to less than 2 / 3 of the OTD, as described above, the length of the narrow segment 8au in the groove depth direction can be increased without significantly impairing the cut-and-separation resistance. This allows for ensuring a large rubber volume and more effectively maintaining wear life.

[0088] It is important to note that, such as Figure 3 As shown, the maximum groove depth (and therefore the groove bottom BOTD of the maximum groove depth) is located in the second shoulder side narrow groove 81c (or 83c) of the narrow groove 81 (or 83) in the width direction; however, the maximum groove depth may be located at other positions in the tread portion 1.

[0089] In other words, the OTD position POTD is the position on an imaginary plane (including the curved surface) parallel to the tread surface 11, perpendicular to the tread surface 11, passing through the bottom BOTD of the groove at the maximum groove depth. However, for the sake of simplicity, in Figure 2 (a) and Figure 2 In (b), it is illustrated along with the tread surface 11 as a straight line. In other words, OTD is the distance between the POTD and the tread surface 11, which are parallel to each other.

[0090] It should be noted that, from the same angle as above, the distance D1 in the groove depth direction between the boundary position of the narrow segment 8bu and the tapered segment 8bt in the narrow groove portion 8b on the tire shoulder side and the OTD position POTD (see...) Figure 2 (b) is preferably 2 / 3 or less of the OTD. Similarly, the distance D1 in the groove depth direction between the boundary position of the narrow segment 8au and the tapered segment 8at in the central side narrow groove 8a and the OTD position POTD (see Figure 2 (a) is preferably 2 / 3 or less of the OTD.

[0091] In the tire 10 of this embodiment, the distance D2 in the groove depth direction between the boundary position of the tapered segment 8at and the wide straight segment 8as in the narrow groove portion 8a on the center side and the OTD position POTD is preferably more than 1 / 6 of the OTD.

[0092] Typically, when the tire wears to a position in the groove depth direction approximately one-third of the OTD from the OTD position POTD (at this point, near a position in the groove depth direction that is about half the groove depth at this time (approximately one-sixth of the OTD from the OTD position POTD), the groove wall expands most significantly towards the interior of the groove during load loading), the incidence of shear separation is particularly high, and thereafter, the incidence of shear separation decreases. Therefore, as described above, by setting the distance D2 in the groove depth direction between the boundary position of the tapered segment 8at and the wide straight segment 8as in the narrow groove portion 8a on the center side and the OTD position POTD to more than one-sixth of the OTD, shear separation is more effectively suppressed.

[0093] In order to fully absorb the crush deformation of the tread rubber 1a and effectively suppress cut separation, when the narrow section 8au and the tapered section 8at are completely worn away and a wide straight section 8as appears on the tread surface 11, under the condition that the tire is mounted on an applicable rim, filled with the specified internal pressure, and under maximum load, the wide straight section 8as should have its groove width W3 and its length D4 in the groove depth direction (see...) Figure 2 (a) is set such that the groove walls of the wide straight section 8as do not contact each other (i.e., the wide straight section 8as do not approach each other).

[0094] In addition, from the perspective of suppressing cutting separation and maintaining wear life, for the wide straight section 8as, its length D4 in the groove depth direction is preferably 0.15 to 0.5 times that of OTD, and from the same perspective, its groove width W3 is preferably 1.5 to 3.0 times that of the groove width of the narrow section 8au (more specifically, the maximum groove width of the narrow section 8au) W1.

[0095] In the tire 10 of this embodiment, the distance D3 in the groove depth direction between the bottom of the central narrow groove portion 8a and the OTD position POTD is preferably less than 1 / 12 of the OTD.

[0096] This allows for a longer length in the groove depth direction of the wide straight section 8as, which can help suppress cut separation and thus suppress cut separation more effectively.

[0097] In the tire 10 of this embodiment, preferably, the groove depth of the shoulder-side narrow groove 8b is shallower than the groove depth of the center-side narrow groove 8a. In other words, the distance D3 in the groove depth direction between the bottom of the shoulder-side narrow groove 8b and the OTD position POTD (see...) Figure 2 (b) is preferably greater than the distance D3 in the groove depth direction between the bottom of the narrow groove 8a on the center side and the OTD position POTD (see Figure 2 (a)

[0098] Therefore, compared to the case where the groove depth of the shoulder-side narrow groove 8b and the groove depth of the center-side narrow groove 8a are the same, the groove depth of the shoulder-side narrow groove 8b is shallower, thereby improving wear life by increasing rubber volume, or the groove depth of the center-side narrow groove 8a is deeper, thereby more effectively suppressing shear separation. In other words, the above-described structure can more effectively maintain wear life and suppress shear separation.

[0099] In this embodiment, the tire 10 is preferably a tire for construction and mining vehicles. Tires for construction and mining vehicles have a high frequency of cuts and separations, and the compatibility between wear life and such cuts and separations is particularly problematic, thus the various effects described above in this embodiment can be demonstrated more effectively.

[0100] Exemplary embodiments of this disclosure have been described above, and various changes may be made without departing from the scope of the claims.

[0101] Example

[0102] The embodiments of this disclosure are described below; however, this disclosure is not limited to the following embodiments.

[0103] The transformation of the tire's circumferential shear strain during rolling was determined by FEM calculations used for the comparative example tire and the inventive example tire. Apart from the construction of the narrow groove 8 in the width direction, the tire has the same... Figures 1 to 3 The tires shown have essentially the same construction. FEM conditions are as follows:

[0104] Tire size: 50 / 80R57

[0105] Wheel rim size: 32.00 / 6.0

[0106] Internal pressure: 700 kPa

[0107] Load: 73 tons

[0108] Wear condition: After 50mm of wear was removed from a 95mm OTD.

[0109] The shape of the narrow groove in the width direction and the groove depth after wear (+50mm are the groove depths when the product is new):

[0110] (Comparative tires) all have Figure 2 The cross-sectional shape shown in (b) and all have a groove depth of 23 mm.

[0111] (Example tires) Each has the above-described features as an embodiment. Figure 1 and Figure 2 The shape shown has a groove depth of 40 mm from the tire equatorial plane CL to the 1 / 8 point P1 / 8, and a groove depth of 23 mm on the outer side of the tire width direction at the 1 / 8 point P1 / 8.

[0112] Under the aforementioned FEM conditions, as referenced above... Figure 4 As stated, it was determined that in Figure 3 The transformation of the circumferential strain (circumferential shear strain) in the belt layer 5f closest to the tread surface 11 in the tire construction (more specifically, between the belt layer 5f near the tire equatorial plane CL and the tread rubber 1a).

[0113] The result is Figure 5 (a) and Figure 5 Provided in (b).

[0114] exist Figure 5 (a) and Figure 5 In (b), the symbol PSI represents the step-in position, the symbol PKO represents the push-out position, and the symbol DS represents the strain difference. That is to say, Figure 5 (a) and Figure 5 The graph in (b) indicates how the circumferential shear strain changes as the tire rolls, including the change from the step-in side to the step-out side. In each graph, the circumferential shear strain (vertical axis) is provided as an exponent.

[0115] Here, the smaller the strain difference DS between the step-in position PSI and the push-out position PKO, the less likely separation progress is to occur.

[0116] according to Figure 5 (a) and Figure 5 The result in (b), when Figure 5 When the strain difference DS in the comparative tire shown in (a) is 100, Figure 5 The strain difference DS in the inventive tire shown in (b) is 95, indicating that the strain difference DS is reduced by 5%. This means that the inventive tire can effectively suppress cut separation.

[0117] Industrial availability

[0118] The tires disclosed herein can be applied to any type of tire, and are particularly suitable for pneumatic tires for construction and mining vehicles, especially tires for construction and mining vehicles used on good roads.

[0119] Explanation of reference numerals in the attached figures

[0120] 1. Fetal face

[0121] 1a Tread rubber

[0122] 2. Side wall portion

[0123] 3. Bead area

[0124] 3a tire bead core

[0125] 4. Fetal body

[0126] 5 belts

[0127] 5a to 5f belt layers

[0128] 7. Circumferential narrow grooves from 71 to 73

[0129] 8. Narrow slots in the width direction, from 81 to 84

[0130] 8a, 81a to 84a Narrow groove on the center side

[0131] Narrow groove on the shoulder side of tires 8b, 81b to 84b

[0132] 81c, 83c second tire shoulder side narrow groove

[0133] 8au, 8bu narrow segment

[0134] 8at, 8bt tapered segments

[0135] 8as wide straight segment

[0136] 8ab, 8bb arc segments

[0137] 9. 91 to 92 Horizontal grooves

[0138] 10 tires

[0139] 11. Tread surface

[0140] BOTD bottom of the maximum groove depth

[0141] CD Tire Circumferential

[0142] CL tire equatorial plane

[0143] Distance in the depth direction from D1 to D3

[0144] D4 Length in the groove depth direction

[0145] DS strain difference

[0146] F load

[0147] GR ground plane

[0148] Maximum groove depth in the OTD tread

[0149] POTD OTD location

[0150] PKO push-off position

[0151] PSI Step-in Position

[0152] P1 / 8 1 / 8 point

[0153] RD tire radial

[0154] TE tread end

[0155] TW tread width

[0156] Slot widths from W1 to W3

[0157] WD (Wheel Width Direction)

Claims

1. A tire, comprising a narrow groove in the width direction extending in a width direction on the tread surface, wherein... The narrow groove in the width direction has a central side narrow groove portion located on the inner side in the tire width direction and a shoulder side narrow groove portion connected to the outer side in the tire width direction of the central side narrow groove portion. In a cross-sectional view perpendicular to the extending direction of the central narrow groove, the central narrow groove is formed from the groove opening side to the groove bottom side into the following continuously connected segments: a narrow segment including the groove opening; a tapered segment whose groove width increases towards the groove bottom; a wide straight segment extending along the groove depth direction with a constant groove width and a groove width greater than that of the narrow segment; and an arc-shaped segment including the groove bottom. In a cross-sectional view perpendicular to the extending direction of the narrow groove on the tire shoulder side, the narrow groove on the tire shoulder side is formed from the groove opening side to the groove bottom side into the following continuously connected segments: a narrow segment including the groove opening; a tapered segment whose groove width increases towards the groove bottom; and an arc-shaped segment including the groove bottom. The narrow slot has a slot width of 3mm to 18mm, or The narrow groove refers to a groove in which, when the tire is mounted on a suitable rim, filled with a specified internal pressure, and under maximum load, the groove walls are at least partially in contact with each other and closed in the groove depth direction.

2. The tire according to claim 1, wherein in the unfolded view of the tread surface, when the tire width direction position obtained by dividing the tread width into 8 equal parts and separating it from the tire equatorial plane is referred to as the 1 / 8 point, the central side narrow groove is disposed in the tire width direction region between the two said 1 / 8 points.

3. The tire according to claim 1 or 2, wherein in a cross-sectional view in the tire width direction, when the maximum groove depth in the tread is referred to as OTD and the location where the bottom of the groove with the maximum groove depth portion is connected in a direction parallel to the tread surface is referred to as the OTD position, the distance in the groove depth direction between the boundary position of the narrow segment and the tapered segment in the center side narrow groove portion and the OTD position is 2 / 3 or less of the OTD.

4. The tire according to claim 1 or 2, wherein in a cross-sectional view in the tire width direction, when the maximum groove depth in the tread is referred to as OTD and the location where the bottom of the groove with the maximum groove depth portion is connected in a direction parallel to the tread surface is referred to as the OTD position, the distance in the groove depth direction between the boundary position of the tapered segment and the wide straight segment in the central side narrow groove portion and the OTD position is 1 / 6 or greater of the OTD.

5. The tire according to claim 1 or 2, wherein in a cross-sectional view in the tire width direction, when the maximum groove depth in the tread portion is referred to as OTD and the location where the bottom of the groove portion having the maximum groove depth is connected in a direction parallel to the tread surface is referred to as the OTD position, the distance in the groove depth direction between the bottom of the groove portion on the center side and the OTD position is 1 / 12 or less of the OTD.

6. The tire according to claim 1 or 2, wherein the groove depth of the shoulder-side narrow groove is shallower than the groove depth of the center-side narrow groove.

7. The tire according to claim 1 or 2, wherein the tire is a tire for construction and mining vehicles.

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